Brush block



Sept. 27, 1960 w. E. STUPAR 2,954,540

BRUSH BLOCK Filed Dec. 12, 1957 INVENTOR.

ATTORNEY WESLEY .STUPAR- Z United States Patent BRUSH BLOCK Filed Dec. 12, 1957, Ser. No. 702,318

4 Claims. Cl. 339-17 This invention relates to a new and improved etched electrical circuit support for .a mechanical component and a method of making the same, and more particularly to a new and improved etched circuit electrical brush block assembly and the method of making the'same.

Heretofore in brush block assemblies, as fol example inbrush blocks for converter disks in analogue to digital converters,the circuit has been printed or etched onto :a -nonconductive base and the contact brushes were then soldered onto the surface of the conductive strip. This required extremely careful and diflicult retention and positioning of the contact wires as they were being soldered'in place. Almost without exception an accurate positioning could not be obtained, and subsequent costly and time-consuming bending and adjustment of the wire brushes was necessary to cause them to touch the surface of the converter disk at the right placev and with the right tension,

The invention provides a means for mounting the contactor wires forming the brush into the brush block, the brush block itself establishing and maintaining the position of the brush wires very accurately, and at the .same time making electrical connection to the electrical terminals which form connectors to othercircuitry.

Briefly described, the brush block and method of assembly embodying my invention is formed first of a nonconductive mounting base, a conductive surface having guide channels formed thereon, preferably by etching. A pro-formed wire brush is positioned in the guide channel :and then clamped to the conductive etched circuit .and mounting'base. The clamping preferably is accomplished by *inserting a rivet through the nonconductive mounting base, the etched circuit, and surrounding the wire, or by soldering, or, if desired, may be done by both. The brush consists of a pair of spaced apart contact legs connected together by a single loop intermediate the ends, Whichassures independent action of the two legs onthe contact surface.

In the drawings: I g

figure 1 is apl-an view of one form of brush block assembly embodying this invention wherein the electrical circuitry forms a mechanical support, a positioning alignment means for the wire contact brushes and also serves as an electrical connector;

Figure 2 is an enlarged cross-sectional View taken on the line 22 of Figure 1;

Figure 3 is an enlarged cross-sectional View taken on the line 33 of Figure 1, and;

Figure 4 is an enlarged detail perspective view of a contact brush block embodying my invention with the parts being broken away to show details of the supporting means.

Referring now to a detailed description of the drawings a brush block assembly embodying my invention is shown by way of illustration, in Figure 1 and in which there are three conductive strips 12, 14 and 20, which for the purpose of illustration are shown in the three steps of assembly taught by applicant, applied to a nonconduca tive block 10. The center conductive strip 12 shows the conductive pattern before the wire brush is in place. The conductive strip 14 shows the same type of conductive strip with a wire contact brush, designated generally by the numeral 16 in place and clamped therein by means of rivet 18. The conductive strip 20 shows a completed conductive strip and brush assembly that has been soldered as at 22.

Each of the conductive strips 12, 14 and 20 are provided with identical conductive patterns surrounding the wire brush 16 and have formed therein a conductive portion 30, which in turn extends into a pair of conductive legs 32. A divider, or island, 34, is provided between the legs 32, as shown in Figures 1, 2 and 4. The conductive strips 12, 14, 20 the portions of the legs 32, the divider 34, and the semicircular conductive portion, 30, 32 and 34 are all :a part of the same conductive pattern produced on the nonconductive block 10 and are produced thereon by means of a conventional photo-chemical etching process which is well known in the art, and, therefore, it is deemed unnecessary for the purpose of simplicity of understanding this specification to be described in detail. It is also to be understood that while for the purpose of describing how this invention operates, that the conductive strips referred to above are applied by means of photo-chemical etching, but that these strips could conceivably be stamped or cut and then applied to the circuit block 10 by means of a suitable clue, without departing from the spirit of this invention. However, it has been found as a practical matter that the most accurate manner, and in this sense accuracy is of one of the essences of this invention, as well as for reasons of economy, to form this con ductive strip isby etching.

At this point it is pointed out that while the thickness of the etched circuitry is not critical, it should be of a suflicient relative depth so as to at least partially surround the legs 40 of the brush, as best illustrated in Figures 2 and 3.

The semicircular conductive portion 30 forms a semicircular guide channel 24 which attaches to a further channel 26 [and in turn connects into a pair of guide channels 28 into which the wire brush 16 is placed.

Each of the conductor strips 12, 14 and 20 are shown terminating in connectors 36 for electrical connections to other circuitry, but it is to be understood that the conductive pattern can contain such circuitry as desired for wiring the entire board and is formed or etched at the same time the conductive strips 12, 14 and 20 are photochemically produced.

The Wire contact brush 16 is pre-formed of a single piece of wire having a loop 37 formed therein intermediate the ends thereto, and is further provided with converging curved portions 38 extending into a path 0t parallel spaced :apart legs 40, which respectively conform to and lay within the guide channels 24, 26 and 28. 'Ilhe legs 40 may, if desired, terminate in V-shaped contact points, or surfaces 42, as shown in Figure 4. The divider, or island, 34, as can be seen best drom Figures 1 and 4, holds the pair of legs 40 of the brush 16 in spaced apart relationship. The retention of the brushes 42 in spaced relationship permits free independent action of the brushes as they make contact with the moving electrical contacts on the converter disk.

In order to further assure rigidity of support and more positive constant electrical contact solder 22, as shown in Figures 1. and 2, is applied over the rivet 18, the conductive legs 32 and the legs 40. Considerable difficulty has been experienced in soldering heavy supported members, such as contact brushes, onto etched circuit blocks by virtue of the fragile nature of the etched circuit, and it has been found that the combination of the rivet 18 clamping the wire brush 16 in place, and at the same time holding the same firmly in position in the channels 28, permits the application of heat to one point such as the rivet 18, from which the conductive heat causes the solder to flow evenly and quickly from the rivet 18 over the legs 40 and the conductive strips 32.

It has been further found that by this practice that peeling or curling of the legs 32 is avoided, outside clamping or holding means are eliminated and general deforming of the etched circuitry is avoided, thereby enabling a rapid, positive, accurate and economical method of suporting, guiding and attaching heavier external members, such as contact brushes to an etched circuit.

As previously pointed out, the advantages of this invention are ease of manufacture, accuracy of positioning the brushes, reproducibility, low cost and permanent spacing support separating the brushes and reliability. The brush block shown in Figure 2 is preferably made from generally available plastic cards, such as melamine, or the like. In practice, copper for the etched circuitry has been found to be quite suitable, although silver, or other low resistance electrical conductive material which lends itself to photochemical etching, can be used.

In the preparation of the etched circuitry a photographic negative which has been carefully prepared to very close tolerances and dimensions can be used to rapidly and cheaply reproduce any desired number of identical brush blocks, with no loss in dimensional accuracy. The use of etched circuit techniques to achieve close tolerances in the location of mechanical components is a further feature of this invention, as well as the feature of using the etched circuit line as a mechanical support.

Although a preferred embodiment of this invention has been illustrated and described herein, it is to be understood that the invention is not limited thereby, but is susceptible of changes in form and detail within the scope of the appended claims.

I claim:

1. A brush block for an analog-to-digital converter comprising a non-conductive block having at least one opening therethrough, a raised conductive pattern formed on one surface of said block, said pattern including a semi-circular portion forming a semi-circular guide channel around said opening and a pair of parallel legs integrally connected therewith, a conductive divider strip between said legs and forming therewith a pair of parallel guide channels, a preformed wire contact brush having a loop extending around said opening and fitting snugly in said semi-circular guide channel and a pair of spaced parallel legs fitting snugly in said parallel guide channels, and clamping means extending through said opening and holding said wire brush firmly in position in said grooves.

2. A brush block for an analog-to-digital converter comprising a non-conductive block having at least one opening therethrough, a raised conductive pattern formed on one surface of said block, said pattern including a semi-circular portion forming a semi-circular guide channel around said opening and a pair of parallel legs integrally connected therewith, a conductive divider strip between said legs and forming therewith a pair of parallel guide channels, a preformed wire contact brush having a loop extending around said opening and fitting snugly in said semi-circular guide channel and a pair of spaced parallel legs fitting snugly in said parallel guide channels, clamping means extending through said opening and holding said wire brush firmly in position in said grooves, and solder intimately bonding said wire brush with adjacent portions of said conductive pattern.

3. A brush block for an analog-to-digital converter comprising a non-conductive block having at least one opening therethrough, a raised conductive pattern formed on one surface of said block, said pattern including a semi-circular portion forming a semi-circular guide channel around said opening and a pair of parallel legs integrally connected therewith, a conductive divider strip between said legs and forming therewith a pair of parallel guide channels, a preformed wire contact brush having a loop extending around said opening and fitting snugly in said semi-circular guide channel and a pair of spaced parallel legs fitting snugly in said parallel guide channels, said wire brush legs extending outwardly beyond one edge of said block and terminating in V-shaped contact points adapted to contact a converter disk, clamping means extending through said opening and holding said wire brush firmly in position in said grooves, and solder intimately bonding said wire brush with adjacent portions of said conductive pattern.

4. A brush block for an analog-to-digital converter comprising a non-conductive block having a plurality of openings therethrough, a raised conductive pattern formed on one surface of said block, said pattern including a semicircular portion forming a semi-circular guide channel around one of said openings and a pair of parallel legs integrally connected therewith, a conductive divider strip between said legs and forming therewith a pair of parallel guide channels, said pattern also including a connector strip integrally connected to said semi-circular portion and extending outwardly therefrom for connection to other circuitry, said connector strip terminating in a circular portion surrounding another of said openings, a preformed wire contact brush having a loop extending around said one opening and fitting snugly in said semi-circular guide channel and a pair of spaced parallel legs fitting snugly in said parallel guide channels, said wire brush legs extending outwardly beyond one edge of said block and terminating in V-shaped contact points adapted to contact a converter disk, clamping means extending through said one opening and holding said wire brush firmly in position in said grooves, and solder intimately bonding said wire brush with adjacent portions of said conductive pattern.

References Cited in the file of this patent I UNITED STATES PATENTS 1,127,088 Platt Feb. 2, 1915 1,648,797 Cohen et al Nov. 18, 1927 1,702,234 Goodridge Feb. 12, 1929 2,127,675 Clements Aug. 23, 1938 2,385,915 Hagedorn et al. Oct. 2, 1945 2,444,599 Genter July 6, 1948 2,547,022 Leno Apr. 3, 1951 2,547,176 Salmons Apr. 3, 1951 2,716,268 Steigerwalt Aug. 30, 1955 2,757,443 Steigerwalt Aug. 7, 1956 

